JP2007325356A - Actuator and manufacturing method for piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator small in size and large in displacement. <P>SOLUTION: The actuator 1 includes: a curved piezoelectric element 30; a supporting member 10 for supporting the piezoelectric element 30; and a driven member 20 attached to the piezoelectric element 30. The piezoelectric element 30 is displaced inward or outward of the curve depending on an applied voltage. The driven member 20 includes: a pair of fixed portions 28 fixed at both ends of the piezoelectric element 30; and a coupling portion 24 coupling the fixed portions 28 with each other. The coupling portion 24 is bent at its head 25 and can be displaced inward or outward of the bend. For this reason, the coupling portion 24 is displaced as follows: it is displaced inward of the bend when the piezoelectric element 30 is displaced inward of the curve; and it is displaced outward of the bend when the piezoelectric element 30 is displaced inward of the curve. The displacement of the coupling portion 24 corresponds to the displacement of the piezoelectric element 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator and a method for manufacturing a piezoelectric element.

As a conventional actuator, for example, as described in Patent Document 1, an actuator including a plurality of rectangular parallelepiped piezoelectric elements and a driven body is known. In such an actuator, when a voltage is applied to a plurality of piezoelectric elements, each piezoelectric element is deformed, and the driven body is displaced according to the deformation of each piezoelectric element.
Japanese Patent Application Laid-Open No. 06-105569

  Since the above-described actuator uses a plurality of rectangular parallelepiped piezoelectric elements, the size becomes large. In order to reduce the size of the actuator, the number of piezoelectric elements may be reduced, but in this case, the displacement of the driven body is reduced.

  Accordingly, an object of the present invention is to provide an actuator having a small size and a large amount of displacement, and a method for manufacturing a piezoelectric element used in the actuator.

  The actuator according to the present invention has one end and the other end, and at least a region between the one end and the other end is curved, and the one end and the other end are curved inward depending on the applied voltage. Alternatively, the piezoelectric element that is displaced outward, a support member that supports a curved region of the piezoelectric element, a pair of fixing parts that are fixed to one end and the other end of the piezoelectric element, and a pair of fixing parts are coupled. A driven member having a bent or curved connecting portion, and the connecting portion is displaced inward or outward of the bent or bent portion of the connecting portion in accordance with displacement of the piezoelectric element. .

  The piezoelectric element used in the actuator of the present invention is formed by bending a region between one end and the other end. By bending the piezoelectric element, a piezoelectric element having a longer effective length can be accommodated in a narrower space. Since the piezoelectric element can be accommodated in a narrow space, the size of the actuator can be reduced. In addition, since the effective length of the piezoelectric element can be increased, the amount of displacement at one end and the other end of the piezoelectric element when a voltage is applied can be increased.

  The piezoelectric element is displaced in the inner and outer directions of the curve according to the applied voltage. The connecting portion of the driving member is bent or curved, and is displaced inward or outward of the bending or bending as the piezoelectric element is displaced. Therefore, when the piezoelectric element is displaced, the connecting portion is displaced inward or outward of the bending or bending by an amount corresponding to the displacement amount of the piezoelectric element. As described above, since the displacement amount of the piezoelectric element having a long effective length is large, the displacement amount of the connecting portion is also large. Therefore, according to the present invention, an actuator having a large displacement can be obtained.

  Furthermore, the piezoelectric element of the present invention is supported by a support member. The support member supports a region between one end and the other end. The displacement between the one end and the other end is very small compared to the one end and the other end. By supporting the portion with a small amount of displacement in this way, the possibility that the support member hinders the displacement of the piezoelectric element can be reduced. Therefore, the displacement amount of the piezoelectric element accurately reflects the applied voltage value. Further, the center of gravity of the piezoelectric element is located in a region between the one end and the other end. Since the center of gravity of the piezoelectric element is always supported by the support member, the piezoelectric element can maintain a stable state even when displaced.

  In the actuator of the present invention, it is preferable that the piezoelectric element has a piezoelectric layer that continuously extends from one end portion toward the other end portion and whose thickness direction is a direction from the inner side to the outer side of the curve. By having such a long and continuous piezoelectric layer, the amount of displacement of one end and the other end of the piezoelectric element can be further increased. Further, by setting the thickness direction of the piezoelectric layer to the direction from the inner side to the outer side of the curve, the piezoelectric element can be reliably displaced in the inner direction or the outer direction of the curve.

  In the actuator of the present invention, it is preferable that the piezoelectric element has a plurality of piezoelectric layers, and the plurality of piezoelectric layers are stacked along a direction from the inner side to the outer side of the curve. In this case, the piezoelectric element can be displaced more greatly inward or outward of the curve.

  In the actuator of the present invention, the piezoelectric element has an internal electrode formed so as to sandwich the piezoelectric layer, and an external electrode connected to the internal electrode, and the external electrode is one end of the piezoelectric element. It is preferable that it is provided in the area | region between the other end part. The external electrode provided in a region where the displacement hardly occurs does not hinder the displacement of the piezoelectric element.

  In the actuator of the present invention, it is preferable that the piezoelectric element has a semi-annular shape. By adopting a semi-annular shape, the piezoelectric element can be smoothly displaced. Furthermore, the accommodation space for the piezoelectric element can be reliably reduced.

  The method for manufacturing a piezoelectric element according to the present invention is a method for manufacturing a curved piezoelectric element, and a first step of forming a sheet laminate by laminating a plurality of green sheets including a green sheet on which internal electrodes are formed. A second step of cutting the sheet laminate to obtain a strip-shaped sheet laminate, a first firing jig having a curved first wall surface, and a curve along the first wall surface of the first firing jig. A second firing jig having a second wall surface, and a strip-like shape so as to be sandwiched between the first wall surface of the first firing jig and the second wall surface of the second firing jig. A fourth step of disposing the sheet laminate, and a fifth step of firing the strip-shaped sheet laminate disposed between the first wall surface and the second wall surface. In the fourth step, Of the side surfaces of the sheet laminate, a pair of side surfaces along the longitudinal direction and perpendicular to the lamination direction is the first wall And to the second wall facing, characterized by arranging the strip-shaped sheet laminate.

  Since the sheet laminated body cut into the strip shape is sandwiched and fired between the curved first wall surface and the curved second wall surface, a curved piezoelectric element can be obtained. Further, when sandwiching the sheet laminate cut into strips, a pair of side surfaces along the longitudinal direction and perpendicular to the lamination direction among the side surfaces of the strip-like sheet laminate are opposed to the first wall surface and the second wall surface. Therefore, the obtained piezoelectric element has a piezoelectric layer continuously extending along the bending direction. As a result, it is possible to easily manufacture a piezoelectric element having a piezoelectric layer that is formed in a curved shape and continuously extends along the bending direction.

  According to the present invention, it is possible to provide an actuator having a small size and a large amount of displacement, and a method for manufacturing a piezoelectric element used in the actuator.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  FIG. 1 is a front view showing an actuator according to the present embodiment. 2A is a top view showing the actuator according to the present embodiment, and FIG. 2B is a cross-sectional view taken along the line II-II of the actuator shown in FIG. As shown in FIGS. 1 and 2, the actuator 1 includes a support member 10, a driven member 20, and a piezoelectric element 30.

  The support member 10 is adjacent to the bottom wall 12, the first side wall 14 and the second side wall 15 that are substantially perpendicular to the bottom wall 12 and opposed to each other, and the first and second side walls 14 and 15 that are substantially perpendicular to the bottom wall 12. A third side wall 16. At the center of the bottom wall 12, a convex portion 17 is provided that protrudes toward a space surrounded by the first to third side walls 14 to 16. An electrode (not shown) for applying a voltage to the piezoelectric element 30 is provided on the upper surface of the convex portion 17, and the electrode is connected to a wiring (not shown) formed inside the support member 10. , Connected to a voltage source (not shown). The width of the upper surface of the convex portion 17 is sufficiently shorter than the length of the piezoelectric element 30.

  A substantially cylindrical tube portion 18 is provided in the center of the third side wall 16. The cylindrical portion 18 is provided such that its radial direction is substantially perpendicular to the bottom wall 12. The length of the cylindrical portion 18 is shorter than the length of the shaft portion 22 of the driven member 20.

  The driven member 20 includes a shaft portion 22, a connecting portion 24 connected to the shaft portion 22, and a pair of fixing portions 28 connected by the connecting portion 24. The shaft portion 22 is inserted into the cylindrical portion 18 of the support member 10. The tube portion 18 serves as a guide for the shaft portion 22 and ensures that the shaft portion 22 operates in a direction perpendicular to the bottom wall 12. The length of the cylindrical portion 18 is shorter than the length of the shaft portion 22. Therefore, one end portion of the shaft portion 22 protrudes from the cylindrical portion 18.

  The connecting portion 24 is coupled to one end portion of the shaft portion 22. The connecting portion 24 includes a head 25 fixed to the shaft portion 22 and a pair of arms 26 extending from the head 25. As shown in FIG. 2, one end of the head 25 is fixed to the shaft portion 22, and the other end extends in a direction opposite to the third side wall 16 of the support member 10. The other end of the head 25 protrudes outward from the support member 10.

  One end of each arm 26 is connected to one end of the head 25. One arm 26 extends from the head 25 toward the first side wall 14, and the other arm 26 extends from the head 25 toward the second side wall 15. Each arm 26 has a substantially flat shape. Therefore, the connecting portion 24 has a shape bent with the head 25 as a top portion. The pair of arms 26 are hinged via the head 25. By connecting the arm 26 with a hinge, the connecting portion 24 can be displaced inward or outward in the bending direction.

  A fixing portion 28 is attached to the other end portion of each arm 26. Each arm 26 and each fixing portion 28 are hinge-coupled. The fixing part 28 is fixed to the piezoelectric element 30. More specifically, one fixing portion 28 is fixed to one end portion 30a of the piezoelectric element 30 and the other fixing portion 28 is fixed to the other end portion 30b of the piezoelectric element 30 via a known adhesive.

  As shown in FIG. 1, the piezoelectric element 30 is a stacked piezoelectric element having one end 30a and the other end 30b. A region between the one end portion 30a and the other end portion 30b of the piezoelectric element 30, that is, an intermediate portion of the piezoelectric element 30 is curved. An intermediate portion of the piezoelectric element 30 is supported by the convex portion 17 of the support member 10. In addition, since the width of the upper surface of the convex part 17 is sufficiently narrow compared with the length of the piezoelectric element 30, the displacement of the piezoelectric element 30 is not suppressed by the support member.

  FIG. 3 is a perspective view showing the piezoelectric element 30. FIG. 4 is a perspective view of the piezoelectric element 30 when viewed from another direction. The piezoelectric element 30 includes a multilayer body 32, and a first external electrode 34, a second external electrode 36, and a third external electrode 38 formed on the side surface of the multilayer body 32. The multilayer body 32 includes a plurality (eight in this embodiment) of piezoelectric layers 40, a plurality (four in this embodiment) of first internal electrodes 42, and a plurality (two in this embodiment) of second electrodes. The internal electrode 44 and a plurality (two in this embodiment) of third internal electrodes 46 are laminated. The piezoelectric layer 40 continuously extends from one end 30a of the piezoelectric element 30 toward the other end 30b. The thickness direction of the piezoelectric layer 40 is along the direction from the inner side to the outer side of the bending of the piezoelectric element 30. The first to third internal electrodes 42, 44, 46 are formed so as to sandwich the piezoelectric layer 40. The stacking direction of the piezoelectric layer 40 and the first to third internal electrodes 42, 44, 46 depends on the piezoelectric body. Similar to the thickness direction of the layer 40, the piezoelectric element 30 extends along the direction from the inner side to the outer side.

  The laminate 32 has a semi-annular hexahedron. The stacked body 32 includes a pair of main surfaces 32a and 32b, a pair of side surfaces 32c and 32c perpendicular to the pair of main surfaces 32a, and a pair perpendicular to the pair of main surfaces 32a and 32b and sandwiched between the pair of side surfaces 32c and 32c. Side surfaces 32d and 32d. The pair of main surfaces 32 a and 32 b are surfaces that are along the bending direction of the stacked body 32 and are opposed to the stacking direction. The main surface 32 a side is located inside the curve of the piezoelectric element 30, and the main surface 32 b is located outside the curve of the piezoelectric element 30. The pair of side surfaces 32 c and 32 c are surfaces facing the bending direction of the stacked body 32. One side surface 32 c is located at one end 30 a of the piezoelectric element 30, and the other side surface 32 c is located at the other end 30 b of the piezoelectric element 30. The pair of side surfaces 32 c and 32 c are fixed to the fixing portion 28 of the driven member 20. The piezoelectric layer 40 and the first to third internal electrodes 42, 44, 46 are exposed from the pair of side surfaces 32c, 32c and the pair of side surfaces 32d, 32d.

  The piezoelectric layer 40 and the first to third internal electrodes 42, 44, 46 include the piezoelectric layer 40, the third internal electrode 46, the piezoelectric layer 40, the first internal electrode 42, the piezoelectric layer 40, and the third internal electrode. 46, piezoelectric layer 40, first internal electrode 42, piezoelectric layer 40, second internal electrode 44, piezoelectric layer 40, first internal electrode 42, piezoelectric layer 40, second internal electrode 44, piezoelectric layer 40 Are stacked in this order. Among the piezoelectric layers 40, the region 40a is sandwiched between the first internal electrode 42 and the second internal electrode 44 that are adjacent to each other in the stacking direction, and the first internal electrode 42 and the third internal electrode 46 that are adjacent to each other in the stacking direction. The region 40b to be formed becomes a piezoelectric active region. The piezoelectric active regions 40a and 40b expand and contract in the stacking direction of the stacked body 32 when a voltage is applied. The piezoelectric active region 40a and the piezoelectric active region 40b have opposite directions of expansion / contraction. That is, the piezoelectric active region 40b contracts when the piezoelectric active region 40a extends, and the piezoelectric active region 40b extends when the piezoelectric active region 40a contracts. As the piezoelectric active regions 40a and 40b expand and contract in this way, the one end 30a and the other end 30b of the piezoelectric element 30 are displaced inward or outward of the curve.

  First to third external electrodes 34, 36, and 38 are provided on the main surface 32 b and the side surface 32 d of the multilayer body 32. The second and third external electrodes 36, 38 are disposed in the intermediate part of the multilayer body 32, and the first external electrode 34 is disposed so that a part thereof covers the intermediate part of the multilayer body 32. . The first to third external electrodes 34, 36, 38 are composed of base electrodes and terminal electrodes, and are formed by simultaneous firing with the laminate 32. The base electrode serves as a base for forming the terminal electrode. The terminal electrode is electrically connected to the first to third internal electrodes 42, 44, 46 exposed from the side surface 32 d of the multilayer body 32 via the base electrode.

  The piezoelectric layer 40 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The first to third internal electrodes 42, 44, 46 are made of a conductive material mainly composed of Ag and Pd. The base electrodes of the first to third external electrodes 34, 36, and 38 are made of a conductive material that can be electrically connected to the metal constituting the first to third internal electrodes 42, 44, and 46 in an excellent manner. For example, similarly to the first to third internal electrodes 42, 44, 46, it is made of a conductive material mainly composed of Ag, Pd. The terminal electrodes of the first to third external electrodes 34, 36, and 38 are formed by printing a paste mainly composed of Pt on the base electrode.

  Then, with reference to FIGS. 5-9, the manufacturing method of the piezoelectric element 30 which has the structure mentioned above is demonstrated.

  First, a green sheet to be the piezoelectric layer 40 is produced (Step S100). In producing the green sheet, for example, a paste in which an organic binder resin, an organic solvent, and the like are mixed with ceramic powder containing PZT as a main component is produced. Then, a plurality of green sheets are produced by applying the paste on a carrier film by, for example, a doctor blade method.

  Next, a plurality of electrode patterns (numbers corresponding to the number of divided chips described later) corresponding to the first to third internal electrodes 42, 44, 46 are formed on the green sheet. In forming the electrode pattern, for example, a paste in which an organic binder resin and an organic solvent are mixed with a conductive material configured in a ratio of Ag: Pd = 85: 15 is prepared. Then, the paste is screen printed on a green sheet and dried to form a green sheet GS1 on which an electrode pattern EL1 corresponding to the first internal electrode 42 is formed, and an electrode pattern EL2 corresponding to the second internal electrode 44. In addition, the second green sheet GS2 and the third green sheet GS3 on which the electrode pattern EL3 corresponding to the third internal electrode 46 is formed are obtained.

  Next, the green sheets on which the electrode patterns are formed are stacked and laminated to obtain a sheet laminate (step S102). The green sheets are laminated in the order of green sheet GS2, green sheet GS1, green sheet GS2, green sheet GS1, green sheet GS3, green sheet GS1, green sheet GS3, and green sheet GS1. A green sheet on which no electrode pattern is formed may be appropriately laminated between the green sheet GS3 and the green sheet GS1 and between the green sheet GS2 and the green sheet GS1.

  Next, the upper and lower surfaces of the obtained sheet laminate are reversed. More specifically, the sheet laminate is such that the surface on which the electrode pattern of the green sheet GS2 laminated first is not formed is the upper surface and the surface on which the electrode pattern of the green sheet GS1 is laminated is the lower surface. Is reversed. After the reversal, the paste described above is screen-printed on the upper surface of the sheet laminate, and the electrode pattern EL4 corresponding to the base electrode of the first external electrode 34, the electrode pattern EL5 corresponding to the base electrode of the second external electrode 36, and the third An electrode pattern EL6 corresponding to the base electrode of the external electrode 38 is formed (step S103).

  After the electrode pattern is formed on the upper surface, the sheet laminate is cut into chips to obtain a plurality of strip-like sheet laminates (step S104). The obtained strip-shaped sheet laminate is hereinafter referred to as green body LS1. FIG. 6 is an exploded perspective view of the green body LS1. As shown in FIG. 6, in the green body LS1, the green sheet GS1, the green sheet GS3, the green sheet GS1, the green sheet GS3, the green sheet GS1, the green sheet GS2, the green sheet GS1, and the green sheet GS2 are in this order. Are stacked. Electrode patterns EL4 to EL6 corresponding to the base electrodes of the first to third external electrodes 34, 36, and 38 are printed on the main surface 60 of the green body LS1, that is, the exposed surface of the green sheet GS2 located in the uppermost layer. ing.

  The paste described above is attached to the side surface of the obtained green body LS1 by a method such as screen printing or transfer to form electrode patterns EL4 to EL6 corresponding to the base electrodes of the first to third external electrodes 34, 36, and 38. (FIG. 5, step S105). FIG. 7 shows a perspective view of the green body LS1 in which the electrode patterns EL4 to EL6 are formed on the side surfaces. A paste mainly composed of Pt is printed on these base electrodes to form portions to be terminal electrodes of the first to third external electrodes 34, 36, and 38 (FIG. 5, step S106).

  Next, the green body LS1 is fired. In firing the green body LS1, a firing jig is prepared (FIG. 5, step S107). FIG. 8A is a perspective view showing the firing jig, and FIG. 8B is a top view of the firing jig. As shown in FIG. 8, the firing jig 50 includes a first firing jig 52 and a second firing jig 54. The first and second firing jigs 52 and 54 have a substantially annular shape. Both the outer wall surface 52a (first wall surface) of the first firing jig 52 and the inner wall surface 54a (second wall surface) of the second firing jig 54 having such a shape are curved in a substantially circular shape. The diameter of the inner wall surface 54 a of the second baking jig 54 is larger than the diameter of the outer wall surface 52 a of the first baking jig 52. The first and second firing jigs 52 and 54 are made of a material such as zirconia.

  The green body LS1 is disposed so as to be sandwiched between the outer wall surface 52a of the first baking jig 52 and the inner wall surface 54a of the second baking jig 54 (FIG. 5, step S108). More specifically, as shown in FIG. 9A, the green body LS1 is placed along the outer wall surface 52a of the first firing jig 52. At this time, a surface of the green body LS1 opposite to the main surface 60 is opposed to the outer wall surface 52a of the first firing jig 52. After the green body LS1 is placed along the outer wall surface 52a of the first firing jig 52, as shown in FIG. 9 (b), the second firing jig 54 is put over so that the main surface 60 of the green body LS1 is the first. 2 It is made to oppose the inner wall surface 54a of the baking jig 54. As described above, the green body LS1 is arranged such that, of the side surfaces of the green body LS1, the pair of side surfaces along the longitudinal direction and perpendicular to the stacking direction are opposed to the first and second firing jigs 52 and 54.

  As shown in FIG. 9C, the green body LS1 is placed on the firing setter 56 made of zirconia while being sandwiched between the first and second firing jigs 52 and 54. Then, a heat treatment is performed at 400 ° C. for about 10 hours to perform a binder removal process on the green body LS1. After the binder removal, the green body LS1 is fired at 950 ° C. for about 2 hours while being sandwiched between the first and second firing jigs 52 and 54 (FIG. 5, step S109). Thereby, the curved laminated body 32 is formed.

  Next, the first and second firing jigs 52 and 54 are removed and the laminate 32 is taken out. The laminated body 32 is subjected to polarization treatment by applying a predetermined voltage for 3 minutes so that the electric field strength with respect to the thickness of the laminated body 32 becomes 2 kV / mm in an environment of a temperature of 120 ° C. (FIG. 5, step S110). Through the above steps, the piezoelectric element 30 shown in FIG. 3 is completed.

  Here, another manufacturing method of the piezoelectric element 30 will be considered. As another manufacturing method, for example, a method of punching the sheet laminated body obtained in step S103 into the shape of the piezoelectric element 30 and firing the punched body can be considered. However, in this method, a piezoelectric element having a structure as shown in FIG. 3, that is, a curved piezoelectric element, in which a piezoelectric layer is laminated in a direction from the inside to the outside of the curve, is obtained. Is very difficult. This is because, by simply punching from the upper surface of the sheet laminate, a curved shape can be obtained, but a piezoelectric layer laminated in the above-described direction cannot be obtained. In the manufacturing method of the present embodiment, the sheet laminate is first cut into strips and then bent using the first and second firing jigs 52 and 54, so that the piezoelectric element 30 as shown in FIG. Can get to.

  Operation | movement of the actuator 1 provided with the piezoelectric element 30 manufactured through the process of step S100-S110 mentioned above is demonstrated. FIG. 10 is a schematic front view for explaining the operation of the actuator 1. FIG. 10A shows a state in which no voltage is applied to the first to third external electrodes 34, 36, 38 of the piezoelectric element 30. FIG. 10B and FIG. 10C show a state in which a voltage is applied to the first to third external electrodes 34, 36, and 38 of the piezoelectric element 30. The application of voltage to the first to third external electrodes 34, 36, 38 is performed via electrodes provided on the support member 10.

  When a voltage is applied and the piezoelectric active region 40a of the laminated body 32 contracts and the piezoelectric active region 40b extends by an amount corresponding to the applied voltage value, the piezoelectric element 30 is bent as shown in FIG. It is displaced in the outer direction, that is, in the direction of the main surface 32b. When the piezoelectric element 30 is displaced in the direction of the main surface 32b, the fixed portions 28 of the driven member 20 fixed to both ends of the piezoelectric element 30 move in directions away from each other. When the fixing portion 28 moves in the direction of separating, the other end of each arm 26 hinged to the fixing portion 28 is pulled by the fixing portion 28 and moves in the direction of separating from each other. As a result, the head 25 located between the arm 26 and the arm 26 is displaced in the direction approaching the bottom wall 12 of the support member 10, that is, in the arrow A direction.

  When a voltage is applied and the piezoelectric active region 40a of the multilayer body 32 expands and the piezoelectric active region 40b contracts by an amount corresponding to the applied voltage value, the piezoelectric element 30 is bent as shown in FIG. It is displaced in the inner direction, that is, in the direction of the main surface 32a. When the piezoelectric element 30 is displaced in the direction of the main surface 32a, the fixed portions 28 of the driven member 20 fixed to both ends of the piezoelectric element 30 move in directions approaching each other. When the fixing portion 28 moves in the approaching direction, the other end of each arm 26 hinged to the fixing portion 28 is pushed toward the head 25 by the fixing portion 28 and moves in a direction approaching each other. As a result, the head 25 positioned between the arms 26 is displaced in a direction away from the bottom wall 12 of the support member 10, that is, in the direction of arrow B.

  As described above, the actuator 1 according to the present embodiment includes the piezoelectric element 30 formed to be curved. Since the curved piezoelectric element 30 is used, the piezoelectric element 30 having a longer effective length can be accommodated in a narrower space than in the case of using a rectangular parallelepiped piezoelectric element. Since the piezoelectric element 30 can be accommodated in a narrow space, the size of the actuator 1 can be reduced. Further, since the effective length of the piezoelectric element 30 can be increased, the amount of displacement of the one end portion 30a and the other end portion 30b of the piezoelectric element 30 at the time of voltage application can be increased.

  The piezoelectric element 30 is displaced inward or outward of the curve according to the applied voltage. In accordance with the displacement of the piezoelectric element 30, the fixing portions 28 fixed to both ends of the piezoelectric element 30 approach and separate from each other. When the fixing portion 28 approaches and separates, each arm 26 of the connecting member 24 hinged to the fixing portion 28 moves, and as a result, the head 25 of the connecting member 24 positioned between the arms 26 is displaced. The displacement amount of the head 25 corresponds to the displacement amount of the piezoelectric element 30. As described above, the displacement amount of the piezoelectric element 30 is large. Therefore, the displacement amount of the head 25 is also large.

  The piezoelectric element 30 is supported by the convex portion 17 of the support member 10. The convex portion 17 supports the intermediate portion of the piezoelectric element 30. By supporting the intermediate portion whose displacement is very small compared to the one end portion 30a and the other end portion 30b, the possibility that the convex portion 17 hinders the displacement of the piezoelectric element 30 can be reduced. Furthermore, by making the width of the upper surface of the convex portion 17 sufficiently shorter than the length of the piezoelectric element 30, the displacement of the piezoelectric element (especially, the outward displacement of the curve) may be suppressed by the convex portion 17. It can be made even lower. Therefore, the displacement amount of the piezoelectric element 30 accurately reflects the applied voltage value. Note that the center of gravity of the piezoelectric element 30 is located in the middle of the piezoelectric element 30. Since the convex portion 17 always supports the position of the center of gravity, the piezoelectric element 30 can maintain a stable state even when displaced.

  In the actuator 1 according to this embodiment, the piezoelectric element 30 has the piezoelectric layer 40. The piezoelectric layer 40 continuously extends from one end 30a of the piezoelectric element 30 toward the other end 30b. By having such a long and continuous piezoelectric layer 40, the amount of displacement of the one end 30a and the other end 30b of the piezoelectric element 30 can be further increased. The thickness direction of the piezoelectric layer 40 is a direction from the inside to the outside of the curve of the piezoelectric element 30. Thereby, the piezoelectric element 30 can be reliably displaced in the inner side or the outer side of the curve.

  Further, in the actuator 1 according to the present embodiment, the stacked body 32 of the piezoelectric elements 30 has a plurality of piezoelectric layers 40, and the stacking direction of the piezoelectric layers 40 is along the direction from the inside to the outside of the piezoelectric elements 30. ing. By laminating the plurality of piezoelectric layers 40 in this manner, the piezoelectric element 30 can be displaced more greatly in the inner or outer direction of the curve than in the case where the number of the piezoelectric layers 40 is one. In addition, the driving voltage for obtaining the same amount of displacement can be reduced as compared with the case where there is only one piezoelectric layer 40.

  Further, in the actuator 1 according to the present embodiment, the piezoelectric element 30 includes the first to third internal electrodes 42, 44, 46 formed so as to sandwich the piezoelectric layer 40, and the first to first internal electrodes connected thereto. Three external electrodes 34, 36, and 38, and the first to third external electrodes 34, 36, and 38 are provided in an intermediate portion of the piezoelectric element 30. Since the middle portion of the piezoelectric element 30 is a portion where displacement hardly occurs, the first to third external electrodes 34, 36, and 38 do not hinder the displacement of the piezoelectric element 30. Therefore, a voltage can be applied to the piezoelectric element 30 without hindering displacement.

  In the actuator 1 according to this embodiment, the piezoelectric element 30 has a semicircular shape. By adopting a semi-annular shape, the piezoelectric element 30 can be smoothly displaced. In addition, as compared with the case where a rectangular parallelepiped piezoelectric element is used, the accommodation space of the piezoelectric element 30 can be reliably reduced.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.

  For example, in the present embodiment, the driven member 20 has the following structure. That is, when the piezoelectric element 30 is displaced in the outward direction of the curve, the head 25 is displaced in a direction approaching the bottom wall 12 of the support member 10, and when the piezoelectric element 30 is displaced in the inward direction of the curve, the head 25 is displaced from the bottom wall of the support member 10. The structure is displaced in a direction away from 12. The driven member 20 may have a structure as shown in FIG. 11 or FIG. FIG. 11 is a schematic front view showing a modified example of the driven member 20. In FIG. 11, when the piezoelectric element 30 is displaced in the outward direction of the curve, the head 25 is displaced in the direction away from the bottom wall 12 (arrow B direction), and when the piezoelectric element 30 is displaced in the inward direction of the curve, the head 25 is displaced. The structure which is displaced in the direction approaching 12 (arrow A direction) is shown. FIG. 12A is a schematic front view showing another modified example of the driven member 20, and FIG. 12B is a schematic top view showing another modified example of the driven member 20. FIG. 12 shows a structure in which when the piezoelectric element 30 is displaced, the head 25 is displaced in the direction of arrow C, that is, the direction passing through the space surrounded by the piezoelectric element 30.

  In the present embodiment, the laminated body 32 of the piezoelectric elements 30 has a semicircular shape, but it is sufficient that at least the middle part of the laminated body 32 is curved. In the present embodiment, the connecting portion 24 has a bent shape with the head 25 as the top. By connecting each arm 26 of the connecting portion 24 to a curve, the connecting portion 24 may have a curved shape with the head 25 as a top portion. In this case, by connecting the arm 26 with a hinge, the connecting portion 24 is displaced inward or outward of the curve.

  In the present embodiment, the first to third external electrodes 34, 36, 38 are composed of the base electrode and the terminal electrode. However, the first to third external electrodes 34, 36, 38 are external (for example, bottom). When it is not necessary to solder to the electrode provided on the convex portion 17 of the wall 12, the first to third external electrodes 34, 36, and 38 need only have base electrodes.

  In the present embodiment, the laminated body 32 of the piezoelectric elements 30 includes the eight piezoelectric layers 40. However, the number of the piezoelectric layers 40 is not limited thereto, and may be one or more. The materials used for the piezoelectric layer 40, the first to third internal electrodes 42, 44, 46, and the first to third external electrodes 34, 36, 38 are not limited to those described above.

It is a front view which shows the actuator which concerns on this embodiment. It is the top view and sectional drawing which show the actuator which concerns on this embodiment. It is a perspective view of the piezoelectric element with which the actuator concerning this embodiment is provided. It is a perspective view of the piezoelectric element with which the actuator concerning this embodiment is provided. It is a flowchart for demonstrating the manufacturing method of the piezoelectric element with which the actuator which concerns on this embodiment is provided. It is a disassembled perspective view of a green body. It is a perspective view of the green body in which the electrode pattern was formed in the side surface. It is the perspective view and top view which show a baking jig. It is a perspective view which shows the process of baking a green body. It is a schematic front view for demonstrating operation | movement of the actuator which concerns on this embodiment. It is a schematic front view which shows the modification of a to-be-driven member. It is the schematic front view and schematic top view which show the other modification of a to-be-driven member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Actuator, 10 ... Support member, 20 ... Driven member, 22 ... Shaft part, 24 ... Connection part, 25 ... Head, 26 ... Arm, 28 ... Fixed portion, 30 ... piezoelectric element, 32 ... laminated body, 32a, 32b ... main surface, 32c ... side surface, 32d ... side surface, 34, 36, 38 ... first to third 3rd external electrode, 40 ... piezoelectric layer, 42, 44, 46 ... 1st-3rd internal electrode, 50 ... firing jig, 52 ... 1st firing jig, 54 ... -Second firing jig.

Claims (6)

It has one end and the other end, and at least a region between the one end and the other end is curved, and the one end and the other end are curved inward or outward depending on applied voltage. A piezoelectric element that is displaced to
A support member that supports the curved region of the piezoelectric element;
A driven member having a pair of fixing portions fixed to the one end portion and the other end portion of the piezoelectric element; and a connecting portion that connects the pair of fixing portions and is bent or curved;
With
The actuator is characterized in that the connecting portion is displaced inward or outward of bending or bending in the connecting portion in accordance with displacement of the piezoelectric element.   2. The piezoelectric element according to claim 1, wherein the piezoelectric element has a piezoelectric layer that continuously extends from the one end portion toward the other end portion and whose thickness direction is a direction from the inside to the outside of the curve. The actuator described. The piezoelectric element has a plurality of the piezoelectric layers,
The actuator according to claim 2, wherein the plurality of piezoelectric layers are stacked along a direction from the inside to the outside of the curve. The piezoelectric element has an internal electrode formed so as to sandwich the piezoelectric layer, and an external electrode connected to the internal electrode,
The actuator according to claim 2, wherein the external electrode is provided in a region between the one end portion and the other end portion of the piezoelectric element.   The actuator according to claim 1, wherein the piezoelectric element has a semi-annular shape. A method of manufacturing a curved piezoelectric element comprising:
A first step of laminating a plurality of green sheets including a green sheet on which internal electrodes are formed to form a sheet laminate;
A second step of cutting the sheet laminate to obtain the strip-shaped sheet laminate;
A third step of preparing a first firing jig having a curved first wall surface and a second firing jig having a second wall surface curved along the first wall surface of the first firing jig; ,
A fourth step of arranging the strip-shaped sheet laminate so as to be sandwiched between the first wall surface of the first baking jig and the second wall surface of the second baking jig;
A fifth step of firing the strip-shaped sheet laminate disposed between the first wall surface and the second wall surface;
Including
In the fourth step,
The strip-shaped sheet laminate is arranged so that a pair of side surfaces along the longitudinal direction and perpendicular to the stacking direction of the side surfaces of the strip-shaped sheet laminate are opposed to the first wall surface and the second wall surface. ,
A method of manufacturing a piezoelectric element.

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